[xdp-hints] Re: [PATCH net v3 1/1] igc: read before write to SRRCTL register

[Jesper Dangaard Brouer <jbrouer@redhat.com>]

On 14/04/2023 17.49, Song Yoong Siang wrote:
> igc_configure_rx_ring() function will be called as part of XDP program
> setup. If Rx hardware timestamp is enabled prio to XDP program setup,
> this timestamp enablement will be overwritten when buffer size is
> written into SRRCTL register.
> 
> Thus, this commit read the register value before write to SRRCTL
> register. This commit is tested by using xdp_hw_metadata bpf selftest
> tool. The tool enables Rx hardware timestamp and then attach XDP program
> to igc driver. It will display hardware timestamp of UDP packet with
> port number 9092. Below are detail of test steps and results.
> 
> Command on DUT:
>    sudo ./xdp_hw_metadata <interface name>
> 
> Command on Link Partner:
>    echo -n skb | nc -u -q1 <destination IPv4 addr> 9092
> 
> Result before this patch:
>    skb hwtstamp is not found!
> 
> Result after this patch:
>    found skb hwtstamp = 1677800973.642836757
> 
> Optionally, read PHC to confirm the values obtained are almost the same:
> Command:
>    sudo ./testptp -d /dev/ptp0 -g
> Result:
>    clock time: 1677800973.913598978 or Fri Mar  3 07:49:33 2023
> 
> Fixes: fc9df2a0b520 ("igc: Enable RX via AF_XDP zero-copy")
> Cc: <stable@vger.kernel.org> # 5.14+
> Signed-off-by: Song Yoong Siang <yoong.siang.song@intel.com>
> Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
> Reviewed-by: Jesper Dangaard Brouer <brouer@redhat.com>
> ---

LGTM, thank for the adjustments :-)

Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>

> v2 -> v3: Refactor SRRCTL definitions to more human readable definitions
> v1 -> v2: Fix indention
> ---
>   drivers/net/ethernet/intel/igc/igc_base.h | 11 ++++++++---
>   drivers/net/ethernet/intel/igc/igc_main.c |  7 +++++--
>   2 files changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/igc/igc_base.h b/drivers/net/ethernet/intel/igc/igc_base.h
> index 7a992befca24..9f3827eda157 100644
> --- a/drivers/net/ethernet/intel/igc/igc_base.h
> +++ b/drivers/net/ethernet/intel/igc/igc_base.h
> @@ -87,8 +87,13 @@ union igc_adv_rx_desc {
>   #define IGC_RXDCTL_SWFLUSH		0x04000000 /* Receive Software Flush */
>   
>   /* SRRCTL bit definitions */
> -#define IGC_SRRCTL_BSIZEPKT_SHIFT		10 /* Shift _right_ */
> -#define IGC_SRRCTL_BSIZEHDRSIZE_SHIFT		2  /* Shift _left_ */
> -#define IGC_SRRCTL_DESCTYPE_ADV_ONEBUF	0x02000000
> +#define IGC_SRRCTL_BSIZEPKT_MASK	GENMASK(6, 0)
> +#define IGC_SRRCTL_BSIZEPKT(x)		FIELD_PREP(IGC_SRRCTL_BSIZEPKT_MASK, \
> +					(x) / 1024) /* in 1 KB resolution */
> +#define IGC_SRRCTL_BSIZEHDR_MASK	GENMASK(13, 8)
> +#define IGC_SRRCTL_BSIZEHDR(x)		FIELD_PREP(IGC_SRRCTL_BSIZEHDR_MASK, \
> +					(x) / 64) /* in 64 bytes resolution */
> +#define IGC_SRRCTL_DESCTYPE_MASK	GENMASK(27, 25)
> +#define IGC_SRRCTL_DESCTYPE_ADV_ONEBUF	FIELD_PREP(IGC_SRRCTL_DESCTYPE_MASK, 1)
>   
>   #endif /* _IGC_BASE_H */
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 25fc6c65209b..a2d823e64609 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -641,8 +641,11 @@ static void igc_configure_rx_ring(struct igc_adapter *adapter,
>   	else
>   		buf_size = IGC_RXBUFFER_2048;
>   
> -	srrctl = IGC_RX_HDR_LEN << IGC_SRRCTL_BSIZEHDRSIZE_SHIFT;
> -	srrctl |= buf_size >> IGC_SRRCTL_BSIZEPKT_SHIFT;
> +	srrctl = rd32(IGC_SRRCTL(reg_idx));
> +	srrctl &= ~(IGC_SRRCTL_BSIZEPKT_MASK | IGC_SRRCTL_BSIZEHDR_MASK |
> +		    IGC_SRRCTL_DESCTYPE_MASK);
> +	srrctl |= IGC_SRRCTL_BSIZEHDR(IGC_RX_HDR_LEN);
> +	srrctl |= IGC_SRRCTL_BSIZEPKT(buf_size);
>   	srrctl |= IGC_SRRCTL_DESCTYPE_ADV_ONEBUF;
>   
>   	wr32(IGC_SRRCTL(reg_idx), srrctl);